Cationic dyeable cellulose esters with improved dyeability

ABSTRACT

Shaped articles of cellulose esters, such as cellulose acetate or cellulose triacetate, and a process for dyeing these articles are provided. Sodium tungstophosphate or sodium tungstosilicate is added to a cellulose ester spinning dope in a minor quantity sufficient to promote the dyeability of the article eventually formed from the dope. The resulting additive-containing spinning dope is formed into a shaped article (e.g., staple fiber, filament, film, etc.) and subsequently contacted with an aqueous dyebath containing a cationic dye.

United States Patent 1 1 [111 Forschirm et al. Dec. 9, 1975 [54] CATIONIC DYEABLE CELLULOSE ESTERS 3,504.997 4/1970 Clapham 8/21 WITH lMPROVED DYEABILITY OTHER PUBLICATIONS [75 1 lnvemors: Mex Fomhim" Lake Hiawatha; L. Diserens, The Chemical Technology of Dyeing and wissbrmbah Printing, Vol. 2, p. 94, Reinhold Publ. Corp., l95l. c. E. Mullin, Acetate Silk and Its Dyes. 1921, p. 160, [73] Assignee: Celanese Corporation, New York, D. Van Nostrand Co. Inc.

NY. 22 Filed: Nov. 2 19- Primary ExaminerThomas J. Herbert, .11.

[2|] Appl. No.: 202,661 [57] Shaped articles of cellulose esters, such as cellulose LS. Cl. e or c lo r ac te, and a process f y 5] I t CH 2 264/78 ing these articles are provided. Sodium tungstophosd S D06? DO6P 3/46: phate or sodium tungstosilicate is added to a cellulose l o c ester spinning dope in a minor quantity sufficient to 6 I78 promote the dyeability of the article eventually formed from the dope. The resulting additive- [56] Reta-"Ices cued containing spinning dope is formed into a shaped arti UNITED STATES PATENTS cle (e.g., staple fiber, filament, film, etc.) and subse- 2,871,231 M959 Straley et a1 8/ I62 S quently contacted with an aqueous dyebath containing 2,882,!76 4/l959 Straley et a1. 8/l62 S a cationic dye. 3,145,073 8/l964 Gagliardi 8/162 S 3,387.916 6/1968 Clarke 8/172 x 21 Claims, N0 Drawings CATIONIC DYEABLE CELLULOSE ESTERS WITH IMPROVED DYEABILITY BACKGROUND OF THE INVENTION cellulose triacetate containing certain dyeability iml0 proving compounds which provide an improved dye uptake and light-fastness to articles formed and dyed from the resulting dope and to a process for dyeing these shaped articles in an aqueous dyebath composition containing a cationic dye.

Techniques of forming shaped articles from cellulose esters such as cellulose acetate or cellulose triacetate are well known. Particularly well known is the procedure of dissolving a cellulose ester such as cellulose acetate in an organic solvent, forming the solution into a desired shape (such as by spinning to form a filament, or casting to form a film), and removing the solvent leaving a solid, shaped article. The thus formed shaped articles find widespread usage in the textile field.

One property of cellulose esters of particular interest in the textile field is dyeability including dye uptake, light-fastness and water-fastness of the resulting dyed article. Dyeing of shaped articles of cellulose esters and particularly the acetates has proven to be somewhat difficult. Generally, dyeing of cellulose acetate shaped articles is accomplished by the use of water-insoluble dispersed dyes in an aqueous dyebath. These dispersed dyes require the presence of a surface active agent in the aqueous dyebath. Shaped articles of cellulose acetate dyed in this manner often possess good light-fastness and fair fastness to washing. Some of the known cellulose acetate disperse dyes, however, have a poor fastness when exposed to acidic gases in the atmosphere.

In addition, disperse dyes may not be uniformly dispersed throughout the dyebath which can result in agglomeration of the dye and uneven dyeing of the fabric. Dispersed dyes are held in the fabric lattice due primarily by solubility (as opposed to reaction at specific chemical sites). Thus, these dyes are more susceptible to loss by washing or dry cleaning of the dyed material.

Articles composed solely of cellulose triacetate are dyeable at the boil with dispersed dyes or below the boil using carriers or pressure. The disperse dyes give adequate fastness levels for end use requirements. Because of the wash-and-wear properties possible in a heat-set triacetate, fastness requirements dictate costly dyestuffs for many shades.

To obtain many deep shades in cellulose acetates, the use of carriers or pressure-dyeing is required. Both of these techniques are difficult to control and add to the ultimate cost of the article. Moreover, articles that are dyed utilizing either a carrier or pressure-dyeing may exhibit undesirable shade changes on exposure to light and wash conditions and the dyestuffs in the articles may sublime when heated, such as during ironing.

The use of carriers may lead to diminished fiber strength or abrasion resistance. Also, failure to remove carriers after dyeing can lead to poor washand lightfastness characteristics of the dyed material and impart an unpleasant odor to the material.

It is known in the art to improve or attempt to improve the dyeability of synthetic polymeric materials by adding thereto one or more additives. For example, in U.S. Pat. No. 3,504,997 and British Pat. No. 1,037,990 it is disclosed that a heteropoly acid such as phosphotungstic, phosphomolybdic, silicotungstic, silicomolybdic, phosphotungstomolybdic and silicotungstomolybdie acid may be reacted with a basic dye to form a heteropoly acid-basic dye complex which increases penetration of an anionic fiber with the dye. These resulting complexes are water-insoluble and therefore require the use of a dispersant when used in an aqueous dyebath.

Reaction of a cationic or basic dye with a phospho- .tungstic or phosphomolybdic acid to produce a dye complex is also shown in U.S. Pat. Nos. 2,802,712 and 3,190,850. In the former patent the dye complex is used as a woodstain in an acid amide solvent, while in the latter the dye complex is used in making solid vinylic pigments. U.S. Pat. No. 3,049,994 discloses the reaction of a basic dye with a salt of heteropoly acid to form an insoluble complex used as a dye in a copy duplication process.

These patents generally show that complexes of heteropoly acids with basic dyes are light-resistant and promote dye uptake. However, these complexes are water-insoluble and require the use of a dispersing or suspending agent when utilized in an aqueous dyebath. In addition, these complexes require separate and special handling.

It has also been proposed to improve the dyeability of cellulose esters by adding compounds containing acidic or basic functional groups which attach to the backbone of the cellulose esters. These added acidic or basic functional groups provide sites for the direct attachment by chemical bonding of a basic or acidic dyestuff. For example, in U.S. Pat. Nos. 2,849,330 and 3,019,119, it is disclosed that sulfonic acid groups may be added to cellulose esters such as cellulose acetate or cellulose triacetate to allow the resulting material to be dyed with a suitable cationic dye. U.S. Pat. No. 3,084,990 similarly adds sulfonic or other strong acid groups such as phosphonic acid groups to cellulose derivatives to promote the cationic dyeing of these materials. The acid group provider may be dissolved in a cellulose acetate dope, shaped articles manufactured therefrom and the shaped articles subsequently dyed with an aqueous dyebath containing a cationic dye.

Procedures such as set forth above have not been proven commercially satisfactory. In particular, the addition of the strong acid groups on a cellulose acetate (or cellulose triacetate) backbone adds significantly to the cost of the resulting shaped articles and also substantially cuts down on the possible end uses of the material. In commercial practice these procedures have proven impractical and the use of dispersed dyes with the resultant disadvantages as noted before has therefore been required.

Also, some basic or acid compounds may degrade cellulose esters by basic saponification or acid hydrolysis.

OBJECTS OF THE INVENTION It is an object of this invention to provide shaped articles of cellulose esters which exhibit improved dyeability characteristics.

It is an object of this invention to provide shaped articles of cellulose esters that exhibit increased dyeability with a cationic or basic dye.

It is an object of this invention to provide shaped articles of cellulose esters dyeable with a cationic or basic dye leaving improved light-fastness.

It is an object of this invention to provide a simple, relatively inexpensive process for the dyeing of shaped articles of cellulose esters with a cationic or basic dye to provide light-fast dyed articles.

It is an object of this invention to provide an improved process for the dyeing of shaped articles of cellulose esters utilizing a water-soluble cationic dye without the necessity to add suspending or dispersing agents to the dyebath.

It is a further object of this invention to provide an improved process for the dyeing of shaped articles of cellulose acetate utilizing a cationic dye in a simple manner without the necessity for an intermediate dye complexing step.

SUMMARY OF THE INVENTION These and other objects of the invention are achieved by providing an improved process for the dyeing of shaped articles of cellulose esters comprising: (a) in cluding in a cellulose ester spinning dope a minor quantity of a compound selected from the group consisting of sodium tungstophosphate and sodium tungstosilicate sufficient to promote the dyeability of a cellulose ester article formed therefrom; ('b) forming a shaped article from the said dope; and (c) contacting the shaped article with an aqueous dye bath containing a cationic dye.

In another aspect, the present invention provides a shaped article consisting essentially of a cellulose ester containing a minor quantity of a compound selected from the group consisting of sodium tungstophosphate and sodium tungstosilicate sufficient to promote the dyeability of the article.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The term shaped articles as used in the present invention generally refers to an article of manufacture which has a length which exceeds a transverse dimension, such as yarns, threads, fibers, filaments and staple fibers. The invention is also applicable to films and the like.

The present invention is adapted for use with cellulose esters and is particularly suitable for use with cellulose esters of the lower aliphatic acids, e.g., cellulose acetate and cellulose triacetate. Other cellulose derivatives useful in the present invention include the simple cellulose esters such as benzoate, formate, propionate, butyrate, isobutyrate, acrylate and crotonate, as well as mixtures of simple esters. Cellulose acetate is preferred.

The cellulose ester spinning dope can be formed in any suitable manner known to those skilled in the art. For example, cellulose triacetate can be dissolved in a suitable solvent such as a methylene chloride-methanol solution containing from about 85 to about 95 (by weight) methylene chloride and from about 15 to about 5 (by weight) methanol to form a viscous spinning dope. Similarly, cellulose acetate can be dissolved in a solution containing from about 80 to about 98%, perferably from about 90 to about 97 (by weight) acetone and from about 20 to about 2 preferably from about to about 3 (by weight) water. The spinning dope generally contains from about to 24 preferably from about 21 to 23 (by weight) of the cellulose ester in the spinning dope. Other suitable organic solvents known to those skilled in the art may be utilized in the same manner to form the cellulose estercontaining spinning dope.

A compound selected from the group consisting of sodium tungstophosphate and sodium tungstosilicate (or mixtures of these compounds) is added to the cellulose ester spinning dope in a minor quantity sufficient to promote the dyeability of the article. The compound can, for example, be added to the spinning dope in an amount from about 0.5 to about 5 preferably from about 1 to about 3%, by weight of the cellulose ester in the spinning dope. It has surprisingly been found that the sodium tungstophosphate and sodium tungstosilicate compounds are soluble in the cellulose ester spinning dope. Sodium tungstophosphate is the preferred additive compound.

In the patents noted above concerning the addition of various heteropoly acid or acid salt complexes with basic dyes, compounds such as sodium molybdosilicate and sodium molybdophosphate are commonly considered the equivalent of the corresponding tungsten salt (i.e., sodium tungstosilicate and sodium tungstophosphate). It has been found, however, that the addition of these molybdosilicic and molybdophosphoric acid sodium salts to a cellulose ester spinning dope in the same amount as tungstosilicic and tungstophoric acid sodium salts as in the present invention results in articles which, when dyed, are unstable and turn blue under ultraviolet light. The sodium molybdophosphate and sodium molybdosilicate compounds are therefore unsuitable for use in the present invention.

The cellulose ester spinning dope containing the dyeability promoting compound can then be formed into the desired shaped article by suitable techniques known to those skilled in the art. For example, a continuous filament can be formed by forcing a solution of the spinning dope through a spinneret. The resulting filaments are hardened by evaporating the solvent into warm air. Clear, colorless films of a cellulose ester such as cellulose acetate can be prepared by casting a solution of the spinning dope and a plasticizer in an organic solvent. The solvent is evaporated from the film. Other conventional techniques used in forming shaped articles of a cellulose ester such as cellulose acetate or cellulose triacetate may also be selected. These techniques are generally well-known in the art.

The resulting shaped article is contacted with a cationic dye in an aqueous dyebath. The cationic dyes utilized in the dyestuff composition of this invention can be of any of the known cationic or basic dyes which preferably are present in any of their known water-soluble forms. Suitable basic dyes include the diphenylmethane and triphenylmethane derivatives, rhodamine dyes, azo dyes, anthraquinone dyes, thiazine dyes, ozazine dyes, xanthene dyes, polymethine dyes, azomethine dyes and cyanine dyes. More specifically, representative basic dyes which can be used in this invention include: diphenylmethanes (ketone imines) such as auramine', triarylmethane dyes such as Color Index (hereinafter C.I.) Basic Green 1, C.I. 42,040, fuchsine (C.I. 42,500), resorcine violet (C.I. 43,520), victoria blue (C.I. 44,040), basic violet (C.I. 42,557) (Suppl), rhoduline violet (C.l. 44,520), the basic dyes ofUS. Pat No. 3,021,344, U.S. Pat. No. 3,032,561 and U.S. Pat. No. 2,083,888; xanthene dyes such as Pyronine G (C.l. 45,005), methylene red (C.I. 45,006), Rhodamine S (C.l. 45,050), saccharein (C.l. 45,070), Rhodamine 56 (Cl. 45,105), Rhodamine G (C.I.

45,150), Rhodamine 66 (C1. 45,160), Rhodamine 12GM (C.l. 45,310); acridines such as Acridine Orange NO (C.l. 46,005), Diamond Phosphine 66 (Cl. 46,035), Rheonine AL(C.1. 46,075), methine dyes such as basic red C.l. 48,015, basic red C.l. 48,013, basic violet C.l. 48,020, basic orange C.l. 48,035, basic yellow C.l. 48,055, basic red C.l. 48,070, basic yellow C.I. 48,060, basic yellow C.1. 48,065, basic dyes prepared from 2-methylene-l,3,3-trimethylindoline (Fischers Base) as disclosed in U.S. Pat. No. 2,734,901 and in Synthetic Dyes" by Venkataraman, Academic Press Inc, New York, 1952, vol. 11, page 1174, basic methine dyes as described in British Pat. No. 462,238 and U.S. Pat. No. 2,164,793, basic azatrimethinecyanines dyes such as those disclosed by .1. Voltz in Angew. Chem. (English edition) pages 532-537, October, 1962; thiazole dyes such as Thioflavine T (C.l. 49,005); indamine basic dyes such as basic green C.l. 49,405; azine dyes such as Mauve (C.l. 50,245), Safranine T (C.l. 50,240), basic violet C.l. 50,055, basic blue C.l. 50,306, lnduline 6B Base (C.l. 50,400); oxazine dyes such as basic blue C.l. 51,004, Mendolas Blue C.l. 51,175, basic black C.l. 51,215; thiazine dyes such as methylene Blue C.l. 52,015, basic green C.l. 52,020; azo dyes such as the azo-safranine dyes described in British Pat. No. 942,844 and U.S. Pat. No. 3,121,722, chrysoidine C.l. 11,270, basic brown C.l. 21,010, the basic azo dyes of British Pat. Nos. 459,594, 785,988, 808,713, 894,389, 896,681,

902,728 and U.S. Pat. Nos. 2,022,921; 2,096,318; 2,099,525; 2,238,485; 2,397,927; 2,833,373; 2,864,812; 2,864,813; 2,889,315; 2,906,747; 2,945,849; 2,965,631; 3,020,272; 3,033,847;

3,074,926; 3,079,377; 3,099,652 and 3,099,653; German Pat. Nos. 1,085,276; 1,088,631 and 1,135,589; French Pat. No. 1,295,862; anthraquinone dyes such as the basic violet mono and dicondensation products of quinizarin with 2-dimethylamino-ethylamine or 3- dimethylamino-propyl-amine (British Pat. No. 489,172), the basic dyes disclosed in U.S. Pat. 2,716,655, the basic dyes disclosed in U.S. Pat. 2,153,012, the basic dyes disclosed in U.S. Pat. Nos. 2,701,801 and 2,701,802, the basic dyes of U.S. Pat. Nos. 2.888,467; 2,611,722; 2,737,517; 2,924,609; and 3,076,821; Canadian Pat. No. 624,035; British Pat. Nos. 459,594; 807,214; 824,530; 903,007; 889,374 and 925,111; German Pat. Nos. 714,986; 1,073,129 and 1,082,916; French Pat. No. 1,277,495 and Belgian pat. No. 609,667; nitro basic dyes such as those disclosed in U.S. Pat. Nos. 2,834,793 and 2,934,794; and basic quinophtalone dyes such as those disclosed in U.S. Pat. No. 3,023,212; Sevron Yellow 3 RL (C.l. basic yellow 15) Sevron Orange G (C.l. basic orange 21), Sevron Brilliant Red 46 (C1. basic red 14), Sevron Red GL (C.l. basic red 18), Sevron Blue B (C.l. basic blue 21), Sevron blue 26 (Cl. basic blue 22), Sevron Green B (C.l. basic green 3), Astrazon Yellow 36 (Cl. basic yellow 1 l Astrazon Blue BG(C.1. basic blue 3), Astrazon Blue 3RL (C.l. basic blue 47), Basacryl Yellow 56L (C.l. basic yellow 24), Basacryl Blue GL(C.1. basic blue 54), and Basacryl Blue 3RL (C.1. basic blue 53). Other suitable cationic dyes will be apparent to those skilled in the art.

The cationic dye can be present in the aqueous dyebath in an amount of from about 0.01 to about 1.5, preferably from about 0.02 to about 1, percent by weight of the total bath. In addition, the dyebath may contain small amounts of suitable dye assisting or promoting compounds as known in the art. For example, the dyebath can contain minor quantities of acetic acid (as a pH adjuster) and a nonionic dye assistant such as an alkyl phenol-ethylene oxide condensate or the like.

Dyeing of the shaped articles of the cellulose ester can be performed utilizing known dyeing techniques. For example, the shaped articles can be contacted with the aqueous dyebath at a temperature of about to about 125C, preferably from about to about C., for a time sufficient to dye the articles which can be, for example, from about 0.5 to about 5 hours, preferably from about 1 to about 3 hours. A final rinse is generally used to complete the dyeing operation. Other dyeing techniques as generally used in the commercial dyeing of cellulose esters (albeit utilized with dispersed dyes) may be adapted to the techniques of the present invention. For example, an accelerant such as butyl benzoate or dialkyl phthalate may be added to the dyebath.

The shaped articles of this invention containing sodium tungstophosphate or sodium tungstosilicate have an increased uptake of the cationic dye in comparison with shaped articles not containing these compounds. In this manner, the shaped articles of the present invention are provided with an improved light-fastness and also the ability to pick up larger amounts of dyes. In addition, the present invention provides a commercially applicable process for the dyeing of cellulose acetate or cellulose triacetate with a cationic dye.

The invention will be further described with reference to the following example which is to be considered illustrative of the invention. It should be understood, however, that the invention is not limited to the details of the example.

EXAMPLE A standard acetate dope was selected and used in the following tests. The dope contained about 20 weight cellulose acetate based upon the total weight of the solution in acetone solvent.

Sodium tungstosilicate and sodium tungstophosphate were each added to samples of the cellulose acetate spinning dope in amounts of 0.2, l and 2% by weight of the cellulose acetate in the spinning dope. In each case, the additive, in the form of a powder, was mixed with the cellulose acetate spinning dope at a temperature of about 21C. under mild agitation. In addition, a control sample of the cellulose acetate spinning dope without either of the sodium tun gstophosphate or sodium tung stosilicate additives was utilized. Each of the samples was formed into a film by casting the dope onto a glass plate and allowing the solvent to evaporate at room temperature. Each of the film samples was exposed to microdyeing for 2 hours at 85C. utilizing two different dyes.

1n the first instance, each of the film samples was contacted with an aqueous dyebath containing Sevron Brilliant Red B dye. In the second instance, each of the dyed film samples was contacted with an aqueous dyebath containing Astrazon Blue RL dye. While both dyes are known cationic dyes, the Sevron Brilliant Red B dye is in wider commercial usage than the Astrazon blue 3 M dye. In addition, the Sevron Brilliant Red B dye is a more sensitive dye and therefore more susceptible to fading. The aqueous dyebaths in each instance contained about 0.5 weight percent of dye based upon the total weight of the bath. The dyebaths also contained about 2 g./l. of acetic acid to give a pH of 5.5

7 and 0.5 g./l. of Triton X-l02 (octyl phenoxy diethoxy ethanol) as a dye-assisting additive.

The dyed shaped articles were then subjected to a Carbon Arc Fadeometer test which, as known in the art, is a standard test to measure dye light-fastness and resistance to fading and which utilizes exposure to ultraviolet radiation. The Carbon Arc Fadeometer Test is described in the Technical manual of the American Association of Textile Chemists and Colorists, Vol. 44. Page 378. Test Method 16 A l964 (Howes Publishing Co, New York, New York, I968). The samples were measured after and hours exposure for dye light-fastness with reference to the International Grey Scale. A value of 5 on the International Grey Scale indicates that no color change took place. The results are shown in the Table below:

3. The process of claim 2 wherein said compound is sodium tungstophosphate.

4. The process of claim 3 wherein said cellulose ester is cellulose acetate.

5. The process of claim 3 wherein said cellulose ester is cellulose triacetate.

6. The process of claim 2 wherein said compound is sodium tungstosilicate.

7. The process of claim 6 wherein said cellulose ester is cellulose acetate.

8. The process of claim 6 wherein said cellulose ester is cellulose triacetate.

9. The process of claim 1 wherein said shaped articles of a cellulose ester are filaments.

10. The process of claim 1 wherein said shaped articles of a cellulose ester are films.

Additive Sodium Tungstophosphate Sodium Tungstosilicatc Control wtfXv on weight cellulose acetate 0 27: 1% 29? 0.2% 1% 2% none Sevron Brilliant Red B 5 hours exposure 3 5 4-5 3 L4 5 3 10 hours exposure 2-3 5 4-5 2-3 3 L4 l 3 Astrazon Blue 5 hours exposure 5 5 5 5 5 S 5 l0 hours exposure 5 5 5 5 5 5 5 Each of the dyed film samples containing the sodium tungstophosphate and sodium tungstosilicate additives had a color which was commercially acceptable. The dyed control sample in each case had a color which was not commercially acceptable in that the samples did not have an adequate shade build-upv As may be seen from the Table, the film samples formed from the cellulose acetate dope containing either the sodium tungstophosphate or sodium tungstosilicate additive compound performed at least as well and generally better than the control sample in regard to lightfastness. The Astrazon Blue 3 RL dye is generally too insensitive to reflect the improvement provided by the present invention. An advantage of the present invention is more clearly seen in the test results for the Sevron Brilliant Red B dye.

Samples made of cellulose acetate containing sodium molybdosilicate and sodium molybdophosphate in similar amounts to the above samples show a good cationic dye uptake. Shaped articles made therefrom result in products having commercially acceptable colors. However, the dyed articles are unstable and turn blue in Carbon Arc Fadeometer tests.

We claim:

1. An improved process for dyeing shaped articles of cellulose esters comprising:

a. including in a cellulose ester spinning dope from about 0.5 to about 5 percent by weight of the cellulose ester of a compound selected from the group consisting of sodium tungstophosphate and sodium tungstosilicate;

b. forming a shaped article from the said dope; and

c. contacting the shaped article with an aqueous dyebath containing a cationic dye and a temperature of from about 75 to about 125C.

2. The process of claim I wherein said compound is added to said cellulose ester spinning dope in an amount of from about I to about 3 percent by weight of the cellulose ester.

11. The process of dyeing shaped articles of cellulose acetate comprising:

a. providing in a cellulose acetate spinning dope from about 0.5 to about 5 percent by weight of the cellulose acetate of a compound selected from the group consisting of sodium tungstophosphate and sodium tungstosilicate to promote the dyeability of a shaped article formed therefrom;

b. forming a shaped article from the said cellulose acetate (lope; and

c. contacting the shaped article with an aqueous dyebath containing a cationic dye and a temperature of from about to about 125 C.

12. The process of dyeing shaped articles of cellulose acetate comprising:

a. providing in a cellulose acetate spinning dope from about I to about 3 percent by weight of the cellulose acetate of a compound selected from the group consisting of sodium tungstophosphate and sodium tungstosilicate to promote the dyeability of a shaped article formed therefrom;

b. forming a shaped article from the said cellulose acetate dope; and

cv contacting the shaped article with an aqueous dyebath containing a cationic dye and a temperature of from about to about C.

13. A shaped article consisting essentially of a cellulose ester containing a minor quantity of a compound selected from the group consisting of sodium tungstophosphate and sodium tungstosilicate sufficient to promote the dyeability of the article.

14. The shaped article of claim 13 wherein the compound is sodium tungstophosphate.

15. The shaped article of claim 14 wherein the cellulose ester is cellulose acetate.

16. The shaped article of claim 14 wherein the cellulose ester is cellulose triacetate.

17. The shaped article of claim 13 wherein said compound is sodium tungstosilicate.

18. The shaped article of claim 17 wherein the celluarticle is a filamemlose ester is cellulose acetate 21. The shaped article of claim 13 wherein the shaped article is a film. 19. The shaped article of claim 17 wherein the cellulose ester is cellulose triacetate. 5 20. The shaped article of claim 13 wherein the said 

1. AN IMPROVED PROCESS FOR DYEING SHAPED ARTICLES OF CELLULOSE ESTERS COMPRISING: A. INCLUDING IN A CELLULOSE ESTER SPINNING DOPE FROM ABOUT 0.5 TO ABOUT 5 PERCENT BY WEIGHT OF THE CELLULOSE ESTER OF A COMPOUND SELECTED FROM THE GROUP CONSISTING OF SODIUM TUNGSTOPHOSPHATE AND SODIUM TUNGSTOSILICATE; B. FORMING A SHAPED ARTICLE FROM THE SAID DOPE; AND C. CONTACTING THE SHAPED ARTICLE WITH AN AQUEOUS DYEBATH CONTAINING A CATIONIC DYE AND A TEMPERATURE OF FROM ABOUT 75* TO ABOUT 125:C.
 2. The process of claim 1 wherein said compound is added to said cellulose ester spinning dope in an amount of from about 1 to about 3 percent by weight of the cellulose ester.
 3. The process of claim 2 wherein said compound is sodium tungstophosphate.
 4. The process of claim 3 wherein said cellulose ester is cellulose acetate.
 5. The process of claim 3 wherein said cellulose ester is cellulose triacetate.
 6. The process of claim 2 wherein said compound is sodium tungstosilicate.
 7. The process of claim 6 wherein said cellulose ester is cellulose acetate.
 8. The process of claim 6 wherein said cellulose ester is cellulose triacetate.
 9. The process of claim 1 wherein said shaped articles of a cellulose ester are filaments.
 10. The process of claim 1 wherein said shaped articles of a cellulose ester are films.
 11. The process of dyeing shaped articles of cellulose acetate comprising: a. providing in a cellulose acetate spinning dope from about 0.5 to about 5 percent by weight of the cellulose acetate of a compound selected from the group consisting of sodium tungstophosphate and sodium tungstosilicate to promote the dyeability of a shaped article formed therefrom; b. forming a shaped article from the said cellulose acetate dope; and c. contacting the shaped article with an aqueous dyebath containing a cationic dye and a temperature of from about 75* to about 125* C.
 12. The process of dyeing shaped articles of cellulose acetate comprising: a. providing in a cellulose acetate spinning dope from about 1 to about 3 percent by weight of the cellulose acetate of a compound selected from the group consisting of sodium tungstophosphate and sodium tungstosilicate to promote the dyeability of a shaped article formed therefrom; b. forming a shaped article from the said cellulose acetate dope; and c. contacting the shaped article with an aqueous dyebath containing a cationic dye and a temperature of from about 85* to about 100* C.
 13. A shaped article consisting essentially of a cellulose ester containing a minor quantity of a compound selected from the group consisting of sodium tungstophosphate and sodium tungstosilicate sufficient to promote the dyeability of the article.
 14. The shaped article of claim 13 wherein the compound is sodium tungstophosphate.
 15. The shaped article of claim 14 wherein the cellulose ester is cellulose acetate.
 16. The shaped article of claim 14 wherein the cellulose ester is cellulose triacetate.
 17. The shaped article of claim 13 wherein said compound is sodium tungstosilicate.
 18. The shaped article of claim 17 wherein the cellulose ester is cellulose acetate.
 19. The shaped article of claim 17 wherein the cellulose ester is cellulose triacetate.
 20. The shaped article of claim 13 wherein the said article is a filament.
 21. The shaped article of claim 13 wherein the shaped article is a film. 